1. Field of the Invention
The invention relates to a coupling unit for the operative monitoring of the high-voltage windings and the connected electric output leads in electric high-voltage machines and apparatus, according to the preamble of claim 1.
2. Description of the Related Art
Such a coupling unit is known in principle, as will be explained in greater detail further on referring to FIG. 1. The stator winding of the turbo-generator comprises here a transformer connected between the common Y-point of the winding and ground potential, a low impedance winding of the transformer or an additional high frequency transformer being connected as a measuring impedance. This known coupling unit and the corresponding measuring method are not sensitive enough; it is impossible to discriminate between the individual phases of the high-voltage winding. Although partial discharges in the high voltage insulation of the winding as well as breaking spark currents in the case of possible conductor interruptions or between winding bars and lamination stacks are surge currents of short duration and pulse-like shape, which are easy to determine by high frequency measuring methods the known coupling unit is not yet satisfactory as far as its sensitivity, in particular with respect to partial discharges on the side of the generator output leads.